Hot-melt adhesives are widely used for manufacturing disposal diapers, binding books and packaging various products. Examples of the material of the hot-melt adhesives include Styrene-Butadiene-Styrene block copolymer (referred to as SBS hereinafter), Styrene-Isoprene-Styrene block copolymer (referred to as SIS hereinafter), Ethylene Vinyl Acetate block copolymer (referred to as EVA hereinafter) and Amorphous Poly Alpha-Olefin (referred to as APAO hereinafter). A tackifier in a form of a hydrogenated petroleum resin is blended in the base polymer.
The hydrogenated petroleum resin is produced by a hydrogenation process for hydrogenating a polymer obtained by adding styrene monomer to cyclopentadiene as disclosed in Patent Literature 1, for instance. The hydrogenated petroleum resin is sometimes provided in a form of hemispherical pellets in view of handleability.
Moreover, it is known that an antioxidant is added to the hydrogenated petroleum resin, for instance, as described in Patent Literatures 1 to 4.